420 CC question

[hrdman2luv]

A quick test is to remove the carb & exhaust pipe.
In a dark place shine a strong torch down the plug hole and look for light in the inlet & exhaust.
As for your worry about how it gets undr the valve when closed. it dosen't.
It falls off and drops under the valve when it opens then gets squashed into the seat when the valve closes

I did shine a flashlight under the valves, best angle I could get, and didn't see any. May have just been the angle. But the bubble test showed some open spots. Extremely minimal. So obviously there was some compression loss from the first go round. The second, after doing what I described, was much better. Enough compression to start it. I haven't done a compression test since I put it together the last time. Calling it quits on this one. It's got more issues that I care to take on. And more issues than the owner is willing to pay for.

I do wish he'd let me keep the engine though. I'd like to "tinker" with it. The other shop in town says they've improved their pistons and rings. Thicker rings now.